This invention relates to fluid control valves and, more particularly, to butterfly valves in which a gate is rotatably positioned within a resilient valve seat. Butterfly valves have traditionally included a casing with a central flow passage therethrough, and a gate rotatable therein for selectively opening and closing the flow passage, as exemplified in U.S. Reppert Pat. No. 2,876,984, issued Mar. 10, 1959; U.S. Stillwagon Pat. Nos. 2,912,218 and 2,994,342, issued Nov. 10, 1959 and Aug. 1, 1961, respectively; U.S. Cotterman et al. Pat. No. 3,173,650, issued Mar. 16, 1965; U.S. Black Pat. No. 3,338,551, issued Aug. 29, 1967; U.S. Hanssen Pat. No. 3,346,005, issued Oct. 10, 1967; and U.S. Naylor Pat. No. 3,904,173, issued Sept. 9, 1975. As these patents demonstrate, it is common to provide a valve seat formed of a liner of resilient material within the flow passage to improve the sealing function as well as to protect the casing from the corrosive influence of fluids being conducted.
Notwithstanding the use of such a liner, leakage problems are still present in many butterfly valves. For instance, fluid may have a tendency to seep along a stem portion of the valve or between the valve gate and the liner. The use of O-rings around the stem, or special bushings which are bonded to the liner and which embrace the stem have somewhat alleviated the problem of leakage along the stem, but room for improvement still remains.
As regards leakage between the gate and the liner, special configurations of these members have been proposed to minimize such leakage, but there remains the problem of providing an adequate seal without unduly hampering the installation of the gate into the liner.
As regards such installation, it is often necessary to deform the liner in order to enable insertion of one-piece gate elements therein. The liners are stiff enough to require substantial effort in order to properly install the gate. It would be desirable for such installation to be accomplished with less effort.
It is, therefore, an object of the present invention to minimize or obviate problems of the sort previously discussed.
It is another object of the present invention to provide a novel butterfly valve assembly.
It is further object of the invention to minimize leakage in butterfly valve assemblies.
It is yet another object of the invention to provide a novel butterfly valve assembly which establishes an effective seal and which may be easily assembled.
It is still another object of the present invention to facilitate the insertion of a one-piece gate into a flexible liner.